C.O.D. posted a guide about setting up Windows Home Server as a Free Email Server
Setting up your Windows Home Server as an Email Server is fast, easy, and best of all; it is totally FREE! The best part about is that you can use your Microsoft given WHS hostname as your email address (yourname@xxxx.homeserver.com). There are many commercial packages out there that can accomplish this task very well and some of them even offer a free version for those of us with little money. However, for easy installation and configuration, I recommend using hMailServer. hMailServer is very simple to use and offers many of the features that some expensive packages offer at no cost to you. There are even options for setting up webmail access.Windows Home Server as a Free Email Server